Don't libertarians have very socially progressive views on sexuality tho? Even more than Democrats, if you're counting stuff like decriminalization of prostitution?
My theory is that the actual correlation is something something 'masculineness' - higher aggression/testosterone/lower agreeableness. Libertarians tend to be high on the masculine spectrum, and Democrats low. I suspect higher masculinity is associated with adultery.
I think he's conflating two different idealogical groups. I have noticed a strain of people who identify as libertarian whose most consistent a priori to their views is selfishness.